Phylogenetic comparisons between mammals and reptiles could provide important clues to the function of sleep. Features of sleep, aminergic activity and cholinergic activity common to the reptilian, avian, and mammalian lines are likely to have been present in the stem reptiles. In mammals, the adrenergic cells of the locus coeruleus (LC) and the serotonergic cells of the raphe are tonically active in waking, decrease discharge in non-REM sleep, and are silent in REM sleep. Mammals also possess two cholinergic cell populations that produce the tonic and phasic components of waking and REM. The function or evolutionary history of these discharge profiles is not known. Narcolepsy, depression and REM sleep behavior disorder may result from disturbance of these discharging profiles. Though these immunohistochemically-defined populations are also found in reptiles, their activity has not been recorded in unanesthetized reptiles. The investigators have developed methods for recording brainstem units from a reptile, the common box turtle, Terrapene Carolina, during sleep and waking behaviors. They will identify and characterize the locus coeruleus, raphe, and cholinergic cell groups of the pedunculopontine and laterodorsal tegmentum immunohistochemically and electrophysiologically. They will compare these cells' state-dependent unit activity with that of mammals in order to provide insights into mthe evolutionary significance of sleep.